Refine wording when a folder with an invalid name could not be created
Summary: This is follow-on for D13805 that improves the wording to be less redundant and a little bit clearer.
Test Plan:
Before:
After:
Reviewers: Dolphin, Frameworks, VDG, tmarshall, elvisangelaccio
Reviewed By: Dolphin, elvisangelaccio
Subscribers: markuss, kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D14641